Surface maintenance machines that support a work tool adapted to perform surface maintenance or surface conditioning tasks are, of course, well known. Such surface maintenance machines often have one or more motorized drivers coupled to a floor maintenance work tool for, among others, scrubbing, sweeping, polishing or burnishing. Also common to such machines is the need to set the elevation of the work tool, and/or pressure applied by the work tool, for example a brush, upon a floor or other work surface to be cleaned.
Sometimes the effective area of contact between the work tool and the work surface is referred to as the “pattern.” To adjust the pattern, an operator typically scatters sand, powder or other granular material over a test area, lowers the brush to a lower limit of travel, operates and then raises the brush. The resulting pattern is then measured, and if needed, the lower limit of travel readjusted and the pattern measurement sequence performed over again. More specifically, industrial grade sweeper equipment commonly used a work tool in the form of a rotatable disk-type brush or rotatable drum-type brush. As can be easily understood for drum-type brushes used for such sweepers, as a work tool is lowered toward the floor the pattern increases as the bristles of a brush are bent or compressed toward the work surface. The brush pattern is of course dependent upon the resiliency of the brush bristles extending radially from the brush drum of a drum-type brush or the bristles extending transversely from a disk of a disk-type brush. This is the same scenario for cylindrical or drum-type brushes as well as all type of tools which move over a work surface. A common feature of such tools is a medium having a working edge portion that continuously wears thus decreasing the size of the pattern. This requires occasional adjustment of the tool to restore the pattern to its desired size.
As is known in the art, in order to consistently sweep a work surface an optimum adjustment of the work tool relative to the work surface is desirable. In the case of horizontally oriented drum-type brush assemblies, the spacing of the axis of rotation of the brush relative to the work surface largely determines brush pattern and resulting magnitude of downward pressure (or “downforce”) that is applied to the work surface by the brush.
A tool, such as a drum-type brush, commonly is partially supported at some elevation above the work surface. When released from a support position, the state of the tool is termed “free float” which is useful for temporarily applying added downforce to a work surface by way of a controllable pivot-type mount or mechanism. Since such brushes are wear items—as the bristles gradually wear down over time—if the pattern is too large (i.e. the brush is applying too great a downforce) the ends of the bristles will rapidly and needlessly erode, damage to the work surface may occur and unnecessary stresses may be applied to a motor and mechanical components configured to power the brush. Indeed, with a pivot-type mount for such drum-type brushes, the brush may auger into the work surface with potential damage to the machine, the work surface and the operator.
More importantly, however is that as the bristles wear, the brush pattern gets smaller resulting in less of the work surface being cleaned as a vehicle is transported over the work surface.
In the past, an operator would manually adjust the spacing of the brush relative to the work surface based largely on a subjective evaluation of the proper spacing and on the operator's experience with the machine. The operator would set an initial spacing between the brush and the work surface. Then, with the brush rotating but the surface maintenance machine stationary, the operator would lower the brush, and sweep a small test area having a test material such as sand, powder, debris or the like strewn on the surface. After retracting the brush, the brush pattern (i.e., the area where the debris was removed) would be manually measured. For a properly calibrated brush assembly, the pattern should comprise an elongated area free of the test material approximately two and a half to three inches in width for the entire axial length of the drum-type brush. If measurement indicates that the pattern is too large or too small, thus indicating a non-optimum setting of the spacing of the brush from the work surface, the operator then would readjust the spacing and begin another iteration to properly set the spacing. This sequence may need to be repeated two or more times with the operator manually adjusting, testing and measuring to determine if the brush is properly adjusted. Because the ends of the bristles of the brush wear down during normal use over time this manual calibration sequence for adjusting the brush relative to the work surface is performed throughout the life of the brush.
A need thus exists in the art for a simple and reliable apparatus for use in accurately setting the spacing of a brush assembly relative to a work surface.
Furthermore, a need exists in the art for effective techniques and methods of fabricating and operating such an apparatus in conjunction with a wide variety of surface maintenance vehicles, including both propelled and walk-behind vehicles.